1. Field of the Invention
This invention relates to an embedded magnet type rotor for use in a rotary electric device such as an electric motor, a generator, or the like, and particularly relates to an embedded magnet type rotor made by a process in which resinous magnet is filled in slits provided in a rotor core such as a laminated iron core, the core having a shape capable of preventing rotation of the rotor core within a manufacturing device, and further relates to a filling method suited for manufacturing the same.
2. Description of the Related Art
Heretofore, an embedded magnet type rotor has been known in which anisotropic resinous magnet is filled in arcuate slits provided in a cylindrical rotor core, circumferentially in regular intervals.
In manufacturing the conventional embedded magnet type rotor, a metallic mold, comprising an upper die and a lower die, is used for filling the resinous magnet. The lower die has permanent magnets disposed along the outside circumference of the rotor core at intervals the same as those of the slits. Ferromagnetic materials are disposed between the permanent magnets. The upper die is placed on the top of the lower die and has gates through which the resinous magnet is filled in the slits.
The rotor core is loaded on the lower die with ends of the arcuate slits directed toward the magnets. Resinous magnet material is filled in the slits while being magnetically orientated. Then, the filled resinous magnet is magnetized using a magnetizing device.
However, an embedded magnet type rotor has magnetic saliency. Thus, in the conventional embedded magnet type rotor, a rotation force is exerted on the rotor core loaded on the metallic mold due to saliency of the magnets of the metallic mold and the rotor core. This force may cause rotation of the rotor core within the metallic mold with the result that the gates of the upper die and the slits of the rotor core are displaced. Therefore, the flow of the resinous magnet in the slits may change during filling, which may result in defective filling of the resinous magnet in the slits.
Even if the resinous magnet can be filled in the slits without trouble, displacement of the rotor core from the initial position during loading will prevent proper orientation of the resinous magnet, resulting in a high rate of misorientation. In addition, reluctance torque due to a magnetization current is produced in a magnetizing process. The reluctance torque may cause rotation of the rotor core within the magnetizing device, which may result in a high rate of defective magnetization.
The problem in magnetization is not limited to anisotropic resinous magnet, but the same trouble is found in isotropic resinous magnet as well.
In view of the foregoing problem, a need existed for an embedded magnet type rotor capable of preventing rotation of the rotor core within a manufacturing device.
One aspect of embodiments of the present invention is an embedded magnet type rotor made by a process in which resinous magnet is filled in slits provided in a rotor core. An inside circumferential surface of a shaft hole formed in the rotor core includes a rotor core side fitting section that is engageable with a manufacturing device side fitting section formed in a manufacturing device for use in an orientating process or a magnetizing process of the resinous magnet.
Another aspect of embodiments of the present invention is an embedded magnet type rotor made by a process in which resinous magnet is filled in slits provided in a rotor core. An outside circumferential surface of the rotor core is provided with a rotor core side fitting section engageable with a manufacturing device side fitting section formed in a manufacturing device for use in an orientating process or a magnetizing process of the resinous magnet.
In preferred embodiments in accordance with the foregoing aspects of the present invention, the rotor core side fitting section is engaged with the manufacturing device side fitting section so that rotation of the rotor core within the manufacturing device can be prevented. Therefore, the resinous magnet can be filled in the slits without trouble, and the resinous magnet can be orientated and magnetized reliably. This process results in a decreased rate of defective cores.
In particularly preferred embodiments in accordance with the foregoing aspects of the present invention, a recessed portion or a projecting portion may be provided as the rotor core side fitting section. The recessed portion is advantageously a groove that runs from one end of the rotor core to the middle thereof or that runs from one end to the other end of the rotor core. When a recessed portion is provided as the rotor core side fitting section, the manufacturing device side fitting section may be provided with a projecting portion engageable with the recessed portion of the rotor core. For example, the projecting portion of the fitting section may comprise a rib extending from one end of the rotor core to the middle thereof or extending from one end to the other end of the rotor core. Preferably, the rib corresponds to the shape of the groove of the rotor core. Alternatively, the projecting portion may be a projection adapted to be protruded within the groove of the rotor core.
Conversely, the rotor core side fitting section may include the projecting portion, and the manufacturing device side fitting section may include the recessed portion.
In alternative embodiments of the present invention, the recessed portion or the projecting portion may be provided as the rotor core side fitting section. In particular embodiments, the recessed portion may be a hole. Alternatively, the recessed portion may be a groove that runs from the shaft hole of the rotor core to the outside circumference thereof. When the recessed portion is provided as the rotor core side fitting section, the manufacturing device side fitting section is advantageously provided with a projecting portion engageable with the recessed portion of the rotor core. For example, the projecting portion may be a projection, or the projecting portion may be a rib that extends from the shaft hole of the rotor core to the outside circumference thereof. Alternatively, the groove may be provided as the rotor core side fitting section, and the projection projecting within the groove may be provided as the manufacturing device side fitting section. Further, by utilizing the slits provided in the rotor core, projecting portions engageable with the slits may be provided on the manufacturing device side.
Furthermore, conversely, a projecting portion may be provided as the rotor core side fitting section, and a recessed portion as the manufacturing side fitting section.
Another aspect of embodiments of the present invention is an embedded magnet type rotor made by a process in which resinous magnet is filled in slits provided in a rotor core. At least one of the end faces of the rotor core is provided with a rotor core side fitting section engageable with a manufacturing device side fitting section formed in a manufacturing device for use in an orientating process or a magnetizing process of said resinous magnet.
Another aspect of embodiments of the present invention is an embedded magnet type rotor made by a process in which resinous magnet is filled in slits provided in a rotor core. The rotor core is provided with a shaft. At least one end of the shaft is provided with a rotor core side fitting section engageable with a manufacturing device side fitting section formed in a manufacturing device for use in an orientating process or a magnetizing process of the resinous magnet.
In preferred embodiments in accordance with this aspect of the present invention, the shaft side fitting section of a shaft provided in the rotor core is engaged with the manufacturing device side fitting section so that rotation of the rotor core within the manufacturing device can be prevented. Therefore, the resinous magnet can be filled in the slits without trouble, and the resinous magnet can be orientated and magnetized reliably, resulting in a decreased rate of defective rotor cores.
Another aspect of embodiments of the present invention is a method of filling resinous magnet in slits provided in a rotor core. In accordance with the method, the resinous magnet is filled in the slits using ejector pins inserted in the slits.
Further, in accordance with this aspect of the invention, the resinous magnet can be filled in the slits with ejector pins inserted in the slits of the rotor core so that rotation of the rotor core within the manufacturing device can be prevented. Therefore, the resinous magnet can be filled in the slits without trouble, and the resinous magnet can be orientated reliably. This process results in a decreased rate of defective cores.
The ejector pin may have any shape, such as, for example, a bar-like shape. The ejector pin may also have an outside circumference having the same as the shape of the inside circumference of the slit.
The tips of the ejector pins may be inserted in the slits shallowly, or inserted to the middle thereof, or inserted deeply to the injection mouths of the slits. When the tips of the ejector pins are inserted in the slits to the middle thereof or inserted to the injection mouths of the slits at which the resinous magnet is injected, the ejector pins may be actively drawn out, or the ejector pins may be automatically retracted by injection pressure of the resinous magnet.
Another aspect of embodiments of the present invention is a method of filling resinous magnet in slits provided in a rotor core. Ejector pins are slidable along the inner surfaces of the spaces to be filled. The ejector pins are inserted in the spaces to the injection mouths thereof. Injection material is injected from the injection mouths, and the ejector pins are moved in the direction of retraction in association with injection of the injection material.
In preferred embodiments in accordance with this aspect of the invention, the ejector pins are slidable along the inner surfaces of the spaces to be filled and are inserted in the spaces to the injection mouths thereof so that no displacement of the mouths is produced. In this manner, the injection material can be filled in the spaces to be filled, without trouble.
In addition, the ejector pins can be moved in the direction of retraction in association with injection of the injection material. Such movement decreases pressure inside the die so that injection pressure of the resin can be kept low, thus preventing deformation of the die. The resin can be filled in the die substantially without voids. This results in an increased filling efficiency.